A. Field of the Invention
This invention pertains to the alignment of brushes in electric motors, and in particular, to brushes on relatively small sized electric motors where the brushes are retained in brush holding brackets.
B. Problems in the Art
Direct current (DC) electric motors take many shapes and forms. They can also be constructed to be of a wide variety of sizes and a wide variety of power ratings.
DC electric motors transfer electrical power from the DC power source into mechanical power by utilizing well known principles associated with electric motors.
Many commercially used relatively small electric motors have the following construction. The motor housing encloses the stator comprised of at least two magnets of opposite polarities. The polarity of the magnets creates a magnetic field B in the motor housing. A rotor containing an armature core with a center shaft or axle extends longitudinally through the stator. The armature core is wound in a predetermined pattern forming an armature winding.
Many times the construction of these small motors has one end of the axle extending out of the housing to form the drive end of the motor. The other end of the axle extends out the other end of the housing and has two or more spaced apart conducting segments positioned radially around that axle end. These segments are called commutator segments. One end of the armature winding is attached to one of the commutator segments, and the other end of the winding is attached to another segment.
Electric power in these motors is conveyed to the commutator segments by brushes. Normally, brushes are conducting material positioned adjacent to the rotational commutator segments so that the brushes conductively touch the segments.
To enable access to the brushes, and maintenance and replacement of the brushes, many times they are positioned in brush holding brackets. These brackets are generally at least somewhat adjustable or removable for this purpose. Brushes are, of course, connected to the direct current power supply. Contact to the brushes is the only electrical contact the rotor makes with the power source. By virtue of the law of physics F=ilxB, the rotor experiences an electromagnetic force causing the rotor to turn within the stator to create the mechanical rotational power.
Many of these types of motors utilize an arrangement where the brushes are positioned 180.degree. apart from one another. Commutator segments may either be two in number, or could be three or more in number.
It has been found that the most efficient transfer of electrical energy between the brushes and the commutator segments is when the brushes are precisely aligned with another. For example, if the brushes are supposed to be 180.degree. apart from one another, to obtain the most efficient operation and most power from the motor, it is generally best to precisely ensure that they are in such an alignment.
The present invention pertains primarily to those electric motors which have brush holding brackets generally 180.degree. apart and which either are somewhat adjustable or have some play in them. In this case, for any number of reasons, the brush holding brackets, and therefore the brushes, may not be precisely aligned, thereby presenting the efficiency and power problem discussed above.
It is therefore desirable to have an easy, reliable and precise way to align the brush holders or realign the brush holders into precise alignment.
A specific example will help point out the value of such a tool. In radio controlled scale-model race cars, electric motors are utilized that have brush holding brackets of the type previously described. Each bracket is within a framework which can be pivoted on the housing to allow access to the brushes. However, because of this construction and the inevitable manufacturing tolerances, there is generally some play in the final positioning of the brush holders when tightened down for operation of the motor.
Whether one is operating the car competitively or not, any misalignment caused by inaccurate positioning, or other reasons, can hurt the operation of the motor. Particularly in competitive situations, this decrease in motor operation can be significant enough to require realignment of the brush holders.
There is, therefore, a real need in the art for a means and method for quickly, easily, and reliably aligning such brush holders.
It is therefore a primary object of the present invention to provide an electric motor brush alignment tool which allows for easy, quick, reliable and accurate alignment of brush holders.
Another object of the present invention is to provide a tool as above described which is simple to operate, has a minimum number of parts, but is flexible in its use.
Another object of the present invention is to provide a tool as above described which is economical and durable.
These and other objects, features and advantages of the present invention will become more apparent with reference to the accompanying specification and claims.